In the paper and other industries, where a web moves with high velocity over rotating cylinders, the axes of which are parallel, there is often a need of affecting the characteristics, of the moving web or the reciprocatory action between the moving web and the cylinders rotating against it (such as friction or adhesion), during the course of the process and usually by small additions of chemicals. There are several methods of this type in practical operation, of which the most customary involve a finely divided liquid being sprayed from one or several jets towards the moving web or a rotating cylinder.
These methods suffer from a number of deficiencies however. If the moving web is wide, several jets are required to be mounted side by side, there are then great difficulties in obtaining a uniform distribution of the finely divided liquid. The more usual types of jet always run the risk of stoppages, giving rise to operational disturbances. Spraying a finely divided liquid in the air is also a sanitary discomfort if effective screening is not arranged.
Alternative methods, developed for various applications, for instance those having a web to pass through a mist chamber, will not show sufficient efficiency at high web velocities because the finely divided liquid particles cannot penetrate the boundary level surrounding the moving web.
Some existing methods fail to meet the requirements of high speed because their design is not suitable for the flow of suspended particles in air at high speed.
A method of applying liquid particles to a rotating cylinder is described in the U.S. Pat. No. 3,926,716 to Bates. This particularly allows a uniform distribution of chemicals over the width where application is to take place. The method does not however permit application of such small amounts of chemicals as is demanded in many cases.